Field of the Invention
This invention relates to a method for producing a multilayer large pipe having an outer support layer and at least one inner liner layer.
Discussion of Related Art
A method for producing a multilayer large pipe through integral joining and nonpositive, frictional engagement between an outer support layer and an inner liner layer is disclosed in European Patent Office Reference EP 1 827 727 B1. In this case, a flat support sheet and a flat liner sheet are placed against each other and then a first connection between the material layers is produced. The material layers which are still resting against each other in a freely movable fashion are then shaped into the pipe with the aid of a bending roller with constant frictional contact between the material layers. After a certain amount of deformation progress, another connection is produced between the material layers so that they are connected to each other in at least one other location. Then, the multilayer pipe undergoes its final shaping with the help of the bending roller and/or a bending machine. After this, it is no longer possible to move the material layers relative to each other and the material layer serving as the inner pipe is pressed with nonpositive, frictional engagement into the material layer serving as an outer pipe. A method that is essentially similar in its production approach is also disclosed by European Patent Office Reference EP 2 285 508 B1, in which at least one of the material layers is composed of more than one applied element.
Other similar methods for producing a multilayer pipe are disclosed in PCT Reference WO 2006/066814 A1 and European Patent Office Reference EP 1 857 194 A1. In all of these methods, flat sheet metal plates for forming the layers are laid onto one another and then attached to each other in alternating fashion in a plurality of steps, the composite is subjected to a first bending process, the layers are tacked to one another again at another location after a certain amount of bending progress, and then bent further in order to produce the multilayer pipe, a process that requires a corresponding amount of production effort.
European Patent Office Reference EP 1 857 194 B1 also discloses a method for producing a multilayer pipe in which first, a flat, plate-shaped support sheet and a flat liner sheet are laid against one another. The support sheet or base sheet is provided with a preferably welded-on stop edge along both of its longitudinal edges or essentially parallel thereto, between which the liner plate is loosely inserted in order for the resulting multilayer material to then be shaped into a multilayer pipe with the help of a bending roller. The material layer serving as an inner pipe is clamped between the stop edges and in the final phase of the pipe shaping in the bending roller and/or a subsequently used bending machine, is pressed with nonpositive, frictional engagement into the material layer serving as the outer pipe. The embodiment of the stop edges and their positioning in accordance with the dimensions of the liner sheet constitute a not insignificant amount of effort in pipe production, and these steps do not achieve an integral connection.
There are also known multilayer large pipes, which are known as clad pipes, are metallurgically plated with a liner layer and are thus already embodied in special production steps in the production process of the plate. With this approach, the material selection is subjected to limits that are too strict for many applications.